The present invention relates to machinery used in foundry processes, and more particularly to a novel foundry apparatus operable for mixing sand with binder ingredients, such as resin and catalyst, in order to produce a composite mixture suitable for foundry molds.
In the art of mixing sand with binder ingredients, it is known to mix sand with resin in one premixing chamber while simultaneously mixing sand with catalyst in another premixing chamber, with the resultant mixtures being brought together for blending in a vertical mixing chamber. Exemplary of that type of apparatus is the construction disclosed in Hulslander et al., U.S. Pat. No. 4,037,826. In that patent, a mixing apparatus is disclosed in which a pair of horizontally positioned premixing chambers are provided with elongate shafts rotatably mounted therewithin which include spiral or helix mixing blades formed as conventional screw-type feeder conveyors.
The premixing chambers transfer, separately, sand mixed with resin and sand mixed with catalyst toward a downstream discharge station. The two mixtures are dispensed downwardly into a vertical mixing chamber which includes a rotator shaft, driven by a motor disposed above the premixing chamber. The vertical mixing chamber includes vertically spaced-apart convoluted blades for mixing the sand introduced from the two premixing chambers. The convoluted mixing blades spiral downwardly and inwardly to mix the material downward through the discharge openings of the mixing chamber.
There are a total of three power sources or motors which are used to drive the mixing apparatus disclosed in the U.S. Pat. No. 4,037,826: one motor for driving the spiral shaft of one of the premixing chambers, another motor for driving the other spiral shaft, and a motor for driving the vertical shaft of the vertical mixing chamber which includes the convoluted mixing blades.
Similarly, Flock et al., U.S. Pat. No. 4,231,664, requires a total of three power sources or motors to operate the mixing apparatus therein disclosed. The U.S. Pat. No. 4,231,664 includes a construction somewhat similar to that of the U.S. Pat. No. 4,037,826, with the exception that the premixing chambers are provided with square shafts having segmented blades formed as a helix for conveying material. However, the U.S. Pat. No. 4,231,664 also discloses the use of a total of three motors for driving the helical shafts as well as the vertical shaft for driving the convoluted blades disposed in the vertically positioned final mixing chamber. The segmented blades are positioned so that when material leaves one trailing edge of a blade, it is subsequently engaged by the leading edge of the next blade positioned 90.degree. away. Thus, material is moved continuously from blade to blade during conveyance along the length of premixing chamber prior to the material being dispensed into the final or vertical mixing chamber.
Another example of an apparatus for making foundry cores is disclosed in Edwards, U.S. Pat. No. 3,580,326, in which parallel and side-by-side positioned feeder-mixer units, including rotatable shafts extending axially therethrough, carry a series of inclined mixing blades. The shafts are driven by a clutch and brake unit operable by a motor which conveys material toward a reaction chamber whereby mixture occurs. The material from the mixer-feeder units is blown into a core box through a blowing head. Obviously, the U.S. Pat. No. 3,580,326 discloses a system in which some type of additional power sources are needed to operate the blowing mechanism.
The above prior art mixing devices contemplate that mixture in the premixing chambers may be effected through a horizontal conveyance of sand and suitable binder material. However, it is disclosed in the above patents that after the mixing of sand with the binder ingredients has occurred, the resultant mixtures must be finally mixed through some type of vertical mixing chamber for dispensing the mixture into a core box or mold. As mentioned above, the various mixing devices which have been discussed contemplate that there are at least several power sources, i.e., it is necessary to drive the auger or bladed shafts of the premixing chambers as well as the shaft of the vertical or final mixing chamber. It is apparent that with multiple power sources, such as motors, downtime for repair and its consequent expense is something which simply cannot be avoided.
Moreover, several of the references, such as the U.S. Pat. Nos. 4,037,826 and 4,231,664, require that the vertical mixing chamber be provided with convoluted blades which are expensive to manufacture. It should also be appreciated that such convoluted blades are difficult to clean, a problem which becomes particularly important to overcome when it is realized that the various binder ingredients which are being mixed together may quickly set up and harden. With convoluted blades there are portions difficult to access for cleaning, and significant downtime may result during cleaning procedures.
The present invention seeks to overcome many of the deficiencies inherent in the prior art mixing apparatus. It is a general object of the present invention to provide a novel apparatus for mixing material, such as particulate matter, with other materials to ensure complete commingling. Specifically, the present invention is directed to a foundry apparatus for mixing sand with binder ingredients to produce a composite mixture suitable for foundry molds or cores which requires the use only of a single power-driven means or motor operable for driving the various components for affecting mixing action. To accomplish this, the present invention utilizes a pair of horizontally-positioned primary mixers, such as first and second premixing means, each of which includes a tubular chamber within which is rotatably driven a bladed shaft operable for conveying and commingling sand with binder ingredients. The premixing means discharge sand with the binder ingredients into a unitary final mixing means which includes a pair of agitator means driven by the bladed shafts of the premixing means. This is accomplished by providing the bladed shafts of each premixing means with extensions which project into the final mixing means. The agitator means are slidably mounted and coupled to the extensions, and thereby rotate therewith.
At a forward end of the final mixing means, there is provided a downwardly extending discharge chute, so that the composite mixture which results from agitation in the final mixing means may be disposed or discharged downwardly into a mold or core box. By aligning the agitator means with the bladed shafts of the premixing means, a single power-driven means or motor may be coupled to the bladed shafts and used to operate the entire apparatus in a mixing sequence.
Another object of the present invention is to provide a pair of premixing means, constructed as above, in which the blades on each shaft are positioned in what may be thought of as a "reverse Archimedes screw." This means that the blade assemblies, which are segmented blades mounted on a square shaft, are positioned in a staggered manner so that they define a reverse helix. This results in what may be thought of as "impulse" mixing during conveyance. Stated differently, it is an object of the present invention to premix sand with binder ingredients so that as the sand and binder ingredients come in contact, they will be mixed together and conveyed forwardly during a rotational sequence of the bladed shaft, but will remain substantially nonconveyed during a subsequent rotational portion and then be conveyed and mixed again.
Still another object of the present invention is to provide a final mixing means, as described above, in which a unitary chamber is provided having semicylindrical sections which communicate with one another. Mounted within each of these semicylindrical sections is an agitator means, coupled to an associated one of the bladed shafts which include paddles sequenced to receive sand and binder ingredient from an associated one of the premixing means and displace that material into contact with sand and binder ingredient material from the other agitator means. Complete commingling of sand and binder ingredient material results in a composite mixture suitable for foundry molds.
Still another object of the present invention is to provide a final mixing means in which a removable end plate may be quickly detached from an end of the unitary chamber to permit access to the agitator means. Moreover, because the agitator means are slidably mounted on an associated extension from the bladed shafts, the agitator means may be quickly removed and cleaned. This becomes particularly important when it is realized that the binder ingredients, emergent with sand from the first and second premixing means, may quickly set up, thus necessitating quick access for disassembly of the components to enable cleaning.
Still another object of the present invention is to provide a base structure for the mixing apparatus in which a drive means, such as a motor, is disposed beneath the horizontally disposed first and second premixing means at a downstream end thereof. A shaft from the motor extends vertically upwardly, and by a suitable worm and gear arrangement is coupled to ends of the bladed shafts operable for rotatably driving each in counterrotation to one another.
These and additional objects and advantages of the present invention will be more readily understood after a consideration of the drawings and the detailed description of the preferred embodiment.